Counting system



Feb. 29, 1944. R. w. PEARsoN Erm. 2,342,753

COUNTING SYSTEM Filed sept. 2v, 1941 ATTORNEY Patented Feb. 2 9, 1944 COUNTING SYSTEM Robert W. Pearson, Wilkinsburg,

Murcek, Duquesne, Pa., house Electric and Ma East Pittsburgh, Pa., a

vania and Slavo J. asslgnors to Westingnufacturing Company,

corporation of Pennsyl- Application September 27, 1941, Serial N o. 412,661

'(lCl. Z50-27) 20 Claims.

Thisinvention relates to a counting system and has particular relation to an electronic system for counting a plurality of moving articles.

In counting slowly moving articles, a system including an electromagnetically operated register energized once for each article under the control of a detecting mechanism, is often employed. However, when the articles are moved at high speeds past the detecting mechanism, the register cannot become deenergized between the detection of successive articles. To avoid faulty operation of the register and permit the articles to be moved at high speeds, an electronic counting system is interposed between the detecting mechanism and the register. The electronic system counts each article, but it operates the register only once for a predetermined number o1' articles. For example, the register may be operated once for each four articles, so that the speed of the moving articles may be four times that permissible when the register is operated once for each article.

An electronic counting system constructed in accordance with the teachings of the prior art employs a plurality of electric discharge devices of the arc-like type. 'I'he detecting mechanism is arranged to supply a potential impulse for each article to render the discharge devices conductive in succession. Each time an impulse is supplied, another discharge device is rendered conductive. When all of the discharge devices become conductive, the register is energized and the system is reset for another cycle of operation. It is then evident that the number of articles which may be counted in one cycle of operation is limited by the number of discharge devices in the system. From another view-point, the number of discharge devices provided must equal the number of articles to be counted in each cycle for any particular application.

It is tobe noted that electronic counting systems of the type described operate satisfactorily in counting the number of articles passing a given point or other events which result in a Vsupply of impulses from the detecting mechaoperated a plurality of times in each counting An ancillary object of our invention is to provide a novel circuit for controlling a series of electric discharge valves.

More specifically, it is an object of our invention to provide apparatus for operating a work device upon a, certain event occurring a predetermined number of times.

In accordance with our invention, a series of electric discharge devices of the arc-like type, preferably thyratrons, are connected in parallel circuits across a source of direct current. These devices may be designated as counting thyratrons, Control circuits for impressing a biasing potential on each counting thyratron to maintain it non-conductive are so arranged that the biasing potential on each thyratron after the first in the series is greater than the biasing potential on the preceding thyratron. A detecting mechanism is provided to impress a potential impulse in the control circuits of the counting thyratrons each time the event to be counted occurs. Each Ipotential impulse supplied from the detecting mechanism is of such polarity as to oppose the ubiasing potentials of the counting thyratrons, but is of such magnitude as to overcome the biasing potential of the first thyratron only, to render it conductive. However, as each thyratron becomes conductive, the current iiowing therethrough causes the biasing potential on each of the succeeding thyratrons to be reduced. The values of the biasing potentials are such that each thyratron is rendered conductive by the next impulse when all of the preceding thyratrons are simultaneously conductive. Each thyratron is also interconnected with the vsucceeding thyratron of the series by coupling means which is operable momentarily as a thyratron is rendered conductive to render all of the preceding thyratrons non-conductive.

However, the coupling permits each thyratron to remain conductive while all of the preceding thyratrons are again rendered conductive in the prescribed manner. Thus, after the rst thyratron is conductive, the second thyratron becomes conductive and the rst thyratron is extinguished. The first thyratron must be rendered conductive again before the third thyratron may become conductive. As the third thyratron becomes conductive, the rst and second thyratrons are extinguished. It is obvious that three more impulses are required to render the iirst and second thyratrons simultaneously conductive, the third thyratron having remained conductive. This order of operation is continued until all of the counting thyratrons are simul`l taneously conductive.

A clearing device, which is also preferably a thyratron, is connected across the source of direct current in parallel with the counting thyratrons. The clearing thyratron is associated with the control circuits of the counting thyratrons in such a manner that it is rendered conductive by the next impulse when all of the counting thyratrons in the series are simultaneously conductive. The clearing thyratron is also coupled with the last thyratron in the series in such a manner that when the clearing thyratron is rendered conductive, all of the counting thyratrons in the series are rendered non-conductive. Another cycle of counting is then initiated by the next impulse. The clearing thyratron remains conductive until the last counting thyratron in the series is rendered conductive, at which time the coupling between the last thyratron and the clearing valve causes the latter to be rendered non-conductive. An electromagnetlcally operated register is arranged to be energized eachvtime the clearing thyratron becomes conductive. Since the clearing thyratron becomes conductive only afterall of thethyratrons in the series are simultaneously conductive, the register is energized once for each cycle of operation.

The novel features that we consider characteristic of our invention are set forth 'with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best'be understood from the following description of a specific embodiment when read in connection with the accompanying drawing, in which:

Figure l is a diagrammatic view illustrating a specific embodiment of our invention: and

Fig. 2 is a table indicating the periods of conductivity of the various discharge devices.

As shown in Fig. 1, a plurality of articles 3 to be counted are carried on a conveyor belt 5 in the direction indicated by the arrow. A detecting mechanism, including a source of light 1 and a photo-sensitive cell 9, is located on opposite sides of the conveyor belt. Power is supplied to the system from a source of alternating current through a transformer I3. One portion l5 of the secondary of transformer |3 is used to energize the light source 1. Another portion I1 of the secondary is used to establish a direct-current potential across a voltage divider I9 through rectifiers 2| and lter capacitors 23 connected in a manner familiar to those skilled in the art.

Light from the source 1 normally impinges .upon the photo-sensitive cell 9, causing current to ow through a circuit extending from an interon the other side. A careful consideration of the y through the cell 9 and a parallel circuit comprising a resistor 21 on one side and a capacitor 29 and resistor 3| on the other side to the negative terminal 33 of the divider. An amplier 35, preferably a pentode tube, has its anode 31 and its cathode 39 connected between a positive terminal 9| and an intermediate terminal 43 of the divider through a resistor 45. The control circuit of the pentode 35 extends from its control electrode 41 through resistor 3| to the negative terminal 33 of the divider and from the intermediate terminal 43 to the cathode 39. While the photo-sensitive cell 9 remains conductive, the biasing potential on the control electrode 41 is such that the anodecathode impedance of the pentode is low. However, when an articlepasses between the source of light 'l and the cell 9, the latter becomes nonconductive and capacitor 29 discharges through resistors 21 and 3|. The current then flowing through resistor 3i develops a potential across the resistor 3| which causes the control electrode l1 of pentode 35 to become more negative with respect to its cathode 39. As a result, the anodecathode impedance of the pentode 35 is greatly increased.

A series of electric discharge counting devices 49, 5| and 53, preferably thyratrons, are connected in parallel circuits between the positive terminal 4| and the intermediate terminal 55 of the divider I9. A clearing device 51, also a thyratron, is likewise connected between the positive terminal 4| and intermediate terminal 55 of the divider. When the first counting thyratron 49 is conductive, current ows from terminal 4| of the divider through a resistor 59, thyratron 49 and resistor 6| to terminal 55. When the second thyratron 5I is conductive, current ilows from terminal 4| of the divider 'through resistor 63,

thyratron 5| and resistor 65 to terminal 55. Curl rent owing from the divider through the third thyratron 53 passes through resistors 61 and 66, and current flowing from the divider through the clearing thyratron 51 passes through resistor 69 and the operating coil 1| of an electromagnetic register 13 in parallel therewith.

A pair oi' resistors 14 and 16 are connected in series with each other between the intermediate terminal 55 and a more negative terminal 18 of the divider |9. The control circuit of the iirst thyratron 49 may then be traced from grid 15 through grid resistor 11, a resistor 19, resistor 14 and resistor BI to the cathode 8|. The control circuit of the second thyratron 5| may be traced from its grid 83 through grid resistor 85, resistor 81 and through a parallel circuit comprising a resistor 89 and resistor 6| on one side and a resistor 9| and resistors 16 and 14 on the other side, and then through a resistor to the cathode 93. 'I'he control circuit of the third thyratron 53 may be traced from its grid 95 through a grid resistor 91 and through parallel circuits and resistor 66 to the cathode |05. The rst of the parallel circuits in the control circuit of the third thyratron extends through a resistor 99 and parallel paths through resistor IUI and resistor 55 on one side and resistor |03 and resistors 16 and 14 on the other side. The second parallel circuit extends through a resistor |91 and parallel paths comprising resistors 89 and 6I on one side and resistors 9|, 16 and 14 control circuits of the counting thyratrons reveais that the biasing potential impressed between the grid and cathode oi' the second thyratron 5| is greater than that between the grid and cathode o! the ilrst thyratron 49. Likewise. the biasing potential between the grid and cathode o! the third thyratron I9 is greater than the biasing potential of the second thyratron I The control circuit of the clearing thyratron 51 is the same as that of thyratron 59, with the exception that the grid resistor 91 of thyratron I9 is replaced by the grid resistor |99 ot the clearing valve 91.

As previously pointed out, the impedance of the pentode 95 is greatly increased each time an article interrupts the light passing from source 1 to the photo-sensitive cell 9. The anode 91 of the pentode 95 is connected to the grids o! counting thyratrons 49, 5| and 99 and clearing thyratron 91 through capacitors and the corresponding grid resistors. The cathode 39 o! the pentode 95 is connected to the cathode. of counting thyratron 49 which in turn is connected to the cathode of thyratron Il through capacitor ||9, the cathode of thyratron 5| also being connected to the cathode of thyratron I9 through capacitor ||4. The functions oi capacitors ||9 and |.|4 will be described hereinafter. Thus, the increase in the potential appearing across the pentode 95 which occurs as its impedance is increased, is impressed as an impulse between the grid and cathode oi each of the counting thyratrons 49, 9| and 59 and the clearing thyratron 51. The potential impulse derived from the pentode 95 is of such polarity as to oppose the biasing potentials of the counting thyratrons and the clearing thyratron, but is of such magnitude as to overcome the biasing potential oi' the iirst thyratron 49 only. However, current owing through the ilrst thyratron 49 after it is rendered conductive by an impulse passes through resistor 9|, whichis in the control circuit of the second thyratron 5|. A potential is then developed across `the resistor 9| which reduces the biasing potential on the second thyratron 5| so that it is rendered conductive by the next impulse from the pentode 95. The potential developed across the resistor 99 when the second thyratron 5| is conductive; and the potential developed across resistor 9| while the rst thyratron 49 is conductive, together, reduce the biasing potential of the third thyratron 59 so that it is rendered conductive by the next impulse when the ilrst and second thyratrons are simultaneously conductive.

A capacitor I I5 and an asymmetric conductor are connected in series between the anode I I9 of the ilrst thyratron 49 and the anode |2| of the second thyratron 5|. The asymmetric conductor comprises a dry rectifier ||1 connected to oer a low resistance to current flowing toward the anode I2| of the second thyratron 5|, and a resistor |29 connected in parallel with the rectiiler to offer a high resistance to current flowing toward the rst thyratron 49. The resistor |29 may be eliminated if a rectier having the correct back resistance is employed. While the ilrst thyratron 49 is conductive, the capacitor ||5 is charged with its negative plate connected to the anode ||9 of the ilrst thyratron by current flowing through resistors 99 and |29, the capacitor and the rst thyratron. Upon the second thyratron 5| becoming conductive, the positive plate of capacitor ||5 is connected through the low resistance oi' rectifier ||1 and thyratron 5| and capacitor ||3 to the cathode 9| of the ilrst thyratron 49. As a result, the rst thyratron 49 is rendered non-conductive. When the next impulse is received from the pentode 39, the ilrst thyratron 49 is again rendered conductive. In the meantime, capacitor Ill has been charged in the opposite direction. However, ,the second thyratron 9| is not rendered non-conductive when the nrst thyratron again becomes conductive, because the high resistance of resistor |29 prevents capacitor il! from applying sumcient potential between the anode |2| and the cathode 99 of the second thyratron 5| to extinguish it.

A capacitor |25 and dry rectiiler |21 with resistor |29 in parallel therewith, are connected between the anodes of the second and third thyrations in the same manner in which capacitor H5, rectier ||1 and resistor |23 are connected between the anodes of the rst and second thyratrons. It is then apparent that when the rst and second thyratrons are simultaneously conductive, the charge on capacitor ||9 approaches zero while capacitor |25 is charged with its negative plate connected to the anodes of the rst and second thyratrons. Upon the third thyratron becoming conductive, the directionof low resistance of rectiflers ||1 and |21 permit the potential of the capacitor |29 to be placed across the anode and cathode of both the ilrst and second thyratron to render them non-conductive. The resistor |29 prevents the third thyratron from being rendered nonconductive while the rst and Segond thyratrons are being rendered conductive again.

The clearing device 51 has its anode |9| coupled to the anode |33 of the third thyratron 59 by a capacitor |95. Capacitor |95 acts in a manner similar to capacitor |25 to extinguish the first, second and third thyratrons as the clearing device is rendered conductive. However, since a rectifier is not connected between the anodes of the third thyratron and the clearing thyratron, the latter is rendered non-conductive when the third thyratron again becomes conductive.

Capacitor |45 is a filter capacitor and the capacitors I|| serve to keep the biasing potentials of the various thyratrons separated and to transmit the potential impulses from the pentode 99 to the grid and cathode of each thyratron. The capacitor ||3 connected between the cathode of thyratrons 49 and 5| permits a small portion of the current flowing through thyratron 49 to pass through the resistor in the cathode circuit of the succeeding thyratron 5|. 'This current develops a potential across the resistor 95 momentarily rendering the cathode 99 of the thyratron 5| more positive, thus preventing the thyratron 5| from being accidently rendered conductive by the sudden surge of current flowing through the resistor 6| in its control circuit when thyratron 49 rst becomes conductive. Capacitor |41 also acts to reduce the eiect of the surge in current through thyratron 49 on the control circuit of thyratron 5|. Capacitor ||4 between thyratrons 5| and 59 and capacitor |49 operate in a similar manner. It is to be noted that the charges on capacitors ||9 and ||4 do not oppose the action of capacitors ||9 and |25. l

The operation of the system may be better understood by referring to the table of Fig. 2 in connection with Fig. 1. To prepare the system for operation push button switch |91 is momentarily closed to connect the `potential source |39 between the grid |4| and cathode |49 of the clearing thyratron to render it conductive and the register is thereafter set to zero. As each article 3 interrupts the light from source 1 to the cell 9, the impedance of the pentode I5 is momentarily increased. v'I'he potential appearing across the pentode 35 is transmitted to the control circuits of its thyratrons so that a plurality of articles interrupting light from the source 1 causes a series of potential impulses to be transmitted to the control circuits. The rst impulse renders the ilrst thyratron 49 conductive. The second impulse renders the second thyratron 5| conductivefat which time the capacitor ||5 causes the first thyratron 49 to become non-conductive. The third impulse again renders the ilrst thyratron 49 conductive, Because of the resistor |23, and rectiiler 1, the second thyratron 5I remains conductive. after the third impulse, the `first and second thyratrons are simultaneously conductive, reducing the biasing potential on the third' thyratron 53 so that the fourth impulse renders it conductive. When the third thyratron 53 ilrst becomes conductive, capacitor |25 causes the ilrst and second thyratrons to be extinguished and capacitor |35 extinguishes clearing thyratron 51. The fth impulse renders the Thus,

iirst thyratron 49 conductive again. The sixth Y impulse renders the second thyratron 5| conductive, and capacitor ||5 at the same time extinguishes the rst thyratron 49 which is then rendered conductive again by the seventh impulse. Thus at the end of seven impulses, all three counting thyratrons 49, 5| and 53 are simultaneously conductive. The eighth impulse causes the clearing thyratron 51 to become conductive, energizing the register 13. The instant the clearing thyratron 51 becomes conductive, the capacitor |35 extinguishes the rst, second and third counting thyratrons, and another cycle of operation is initiated by the next impulse. The third thyratron again becomes conductive upon receipt of the fourth impulse of the second cycle, and capacitor |35 thereupon renders the clearing thyratron 51 non-conductive. The eighth impulse of the second cycle again renders the clearing thyratron conductive to again energize the register 13. Thus the register is reenergzed once for every eight articles counted.

From the foregoing description, it is obvious that the number of thyratrons preceding the clearing valve may be varied, but the number is limited by the ability of the last coupling capacitor to extinguish all of the preceding thyratrons. It is also possible to eliminate the clearing valve 51 and install some other suitable clearing means, such as a series of relays, eil'ective to disconnect the thyratrons from the source when all of the thyratrons are simultaneously conductive. If it is desired to count a large number of impulses in each cycle, several counting systems as described may be arranged in cascade with means responsive to the conductivity of the clearing thyratron of each system to supply impulses to the next system.

Since the counting thyratrons are rendered conductive singly, the total number of impulses required to cause all oi.'y the counting thyratrons to be conductive simultaneously, which shall be designated hereinafter as t, is equal to the sum of the number of times the various counting thyratrons are rendered conductive. Because of the extinguishing arrangement, each counting thyrario ductive simultaneously. The lasithyratron then becomes conductive once, the next to the last thyratron is rendered conductive twice, and the second from the last thyratron is rendered conductive four times and so on for n number of thyratrons. Thus. the sequence of the number of times successive thyratrons become conductive forms a geometric progression in which the rst term, a, equals 1 and the common ratio r equals 2. .As is well known the sum of a geometric progression to cause all of n number of counting thyratrons to be simultaneously conductive. Since the clearing thyratron is rendered conductive by the next impulse after all of the counting thyratrons are simultaneously conductive, the total number of impulses included in a complete counting cycle is equal to 2"--1-l-1 or 2" where n equals the number of counting thyratrons.

Although we have shown and described a spe'- ciiic embodiment of our invention, we are fully aware that many modiilcations thereof are possible. Our invention, therefore. is not to rbe restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

We claim as our invention:

l. In combination, a. source of direct current, a pair of electric discharge devices of the arc-like type connected in parallel circuits across said source, means for rendering said devices conductive singly, and coupling means interconnecting said devices so that the first of said devices is rendered non-conductive upon the second device being rendered conductive later than said first device and the second device remains conductive upon the first device becoming conductive later than said second device.

2. In combination, a source of direct current, a pair of electric discharge devices of the arclike type, each of said devices having a plurality of principal electrodes connected in an individual circuit across said source, means for rendering said devices conductive singly, and coupling means interconnecting said devices so that the rst of said devices is rendered non-conductive upon the second device being rendered conductive later than said first device and the second device remains conductive upon the irst device becoming conductive later than said second device, said coupling means including a capacitor and an asymmetric conductor connected in series with each other between a principal electrode of one device and the corresponding electrode of the other device.

3. In combination, a source of direct current, a pair of electric discharge devices of the arc-like type connected in parallel circuits across said source, means for rendering said devices conductive singly, and coupling means interconnecting said devices comprising extinguishing means conditioned while either of said devices is alone conductive to render said conductive device nonconductive upon the other device being thereafter rendered conductive, and means in circuit with said extinguishing means for preventing it from rendering one of said devices non-conductive but permitting it to render the other device before al1 of the counting thyratrons are con- I4 non-conductive.

v4. In combination, a source oi' direct current, a pair of electric discharge devices of the arc-like type, each of said devices having a pair oi principal electrodes connected in an individual circuit across said source, means for rendering said devices conductive singly, and coupling means interconnecting said devices so that the first of said devices is rendered non-conductive upon the second device being rendered conductive later than said nrst device and the second device remains conductive upon the iirst device becoming conductive later than said second device, said coupling means including a capacitor and a dry rectier connected in series between a principal electrode of the iirst device and the corresponding electrode of the second device with thegrectier oiering its highest resistance to current flowing toward the iirst device.

`5. In combination, a source of direct current, a pair of electric discharge devices of the arc-like type. each of said devices having a pair of principal electrodes connected in an individual circuit across said source, means for rendering said devices conductive singly, and coupling means in` terconnecting said devices so that the nrst of said devices is rendered non-conductive upon the second device being rendered conductive later than said iirst device and the second device remains conductive upon the first device becoming conductive later than said second device, said coupling means including a capacitor and a dry rectier connected in series between a principal electrode of the irst device and the corresponding electrode of the second device with the rectier oiering its highest resistance to current flowing toward the rst device and a resistor connected in parallel with said dry rectifier, said resistor having a resistance less `than the highest resistance of said rectier. y

6, In combination, a source of direct current, a pair of electric discharge devices of the arclike type connected in parallel circuits across said source, control means tending to maintain said devices non-conductive, said control means exerting a stronger iniiuence on the second of said devices than on the iirst device, means for opposing said control means `at intervals, said opposing means being sufficiently strong to overcome the influence oi said control means on said first device only to render it conductive, means responsive to the conductivity of said nrst device for reducing the inuence o! said control means on said second device whereby it is thereafter rendered conductive by said opposing means, and coupling means interconnecting said devices and including extinguishing means conditioned whlle either of said devices is alone conductive to render said conductive device non-conductive upon the other device being thereafter rendered conductive whereby said iirst device is rendered nonconductive when said second device becomes conductive, said opposing means being eiective to against render said rst device conductive, and means for preventing said extinguishing means from rendering said second device non-conductive when said rst device again becomes con ductive.

7. In combination, a source of direct current, a pair of electric discharge devices of the arclike type connected in parallel circuits across said source, control means tending to maintain said devices non-conductive, said control meansexerting a stronger inuence on the second of said devices than onthe rst device, means ior opposing said control means at intervals, said opposing means being suiliciently strong to overcome the innuence ci said control means on said first device only to render it conductive. means responsive tothe conductivity of said rst device for reducing the iniiuence of said control means on said second device whereby it is thereafter rendered conductive by said opposing means, and coupling means interconnecting said devices so that said iirst device is rendered non-conductive upon the second device being rendered conductive, said opposing means being eiiective to again render said first device conductive, said coupling means permitting said second device to remain conductive upon said rst device again becoming conductive.

8. In combination, a source of direct current, a pair of electric discharge devices of the arclike type, each oi said devices having a paix` of principal electrodes connected in an individual circuit across said source, control means tending to maintain said devices non-conductive, said control means exerting a stronger iniiuence on the second of said devices than on the Iirst device, means ior opposing said control means at intervals, said opposing means being sufficiently strong to overcome the influence oi' said control means on said iirst device only to render it conductive, means responsive to the conductivity of said iirst device for reducing the iniiuence of said control means on said second device so that it is thereafter rendered conductive by said opposing means, and coupling means comprising a capacitor and an asymmetric conductor connected in series With each other between a principal electrode of the first and the corresponding electrode or the second device so that said iirst device is rendered non-conductive upon said second device becoming conductive, said opposing means being eiective to again render said nrst device conductive, said coupling means permitting said second device to remain conductive upon said rst device again becoming conductive.

9. In combination, a source of direct current. a pair of electric discharge devices of the arclike type, each having a pair of principal electrodes connected in an individual circuit across said source and a control electrode, control means for impressing a biasing potential between the control electrode and one of the principal electrodes of each device to maintain it non-conductive, the biasing potential on the second of said devices being greater than on the rst device, means for supplying a plurality of spaced potential impulses to oppose said biasing potentials, the magnitude of each of said impulses being sufilcient to overcome the biasing potential on said ilrst device only to render it conductive, means responsive to conductivity of said first device for reducing the biasing potential on said second device so that said second device is rendered conductive by the next impulse after said iirst device becomes conductive, andcoupling means interconnecting said devices so that said ilrst device is temporarily rendered nonfconductive upon the second device being rendered conductive, said coupling means permitting said second device tov remain conductive upon said first device again becoming conductive.

10. The combination comprising a source of direct current, a series of electric discharge Ydevices of the arc-like type connected in parallel circuits across said source, control means tending to maintainsaid `devices non-conductive,' said control means exerting a stronger influence on each device after the ilrst than on the device preceding it, means for opposing said control means at spaced intervals of time, said opposing means being sufdcient to overcome the influence of said control means on the rst of said devices only to render it conductive, means responsive to the conductivity of each device for reducing the iniluence oi.' said control means on each of the succeeding devices so that each device after the rst device is rendered conductive by said opposing means only when all of the preceding devices are simultaneously conductive, and means operable momentarily as each device is rendered conductive to render all of the preceding devices temporarily non-conductive.

11. The combination comprising a source of direct current, a series of electric discharge devices of the arc-like type, each having a plurality oi' principal electrodes connected in an individual circuit across said source and a control electrode, control circuits for said devices including means i'or impressing a biasing potential between the control electrode and one of said principal electrodes of each device to maintain it non-conductive, the biasing potential on each device after the rst in said series being greater than on the preceding device, means for impressing said potential impulses in said control circuits in opposition to said biasing potentials, said biasing potentials being of such magnitude that said impulses counteract the biasing potential on the first device only to render it conductive, means responsive to the conductivity of each device for reducing the biasing potential on each of the succeeding devices so that each device is rendered conductive by the next impulse when all of the preceding devices are simultaneously conductive, and means operable momentarily as each device is rendered conductive to render all of the preceding devices temporarily non-conductive. Y

12. 'I'he combination comprising a source of direct current, a series of electric discharge devices oi the arc-like type, each having a pair of principal electrodes connected in an individual circuit across said source, control means "tending to maintain said'devices non-conductive, said control means exerting a stronger inuence on each device after the rst in said series than on the preceding device, means for opposing said control means at intervals, said opposing means being suillcient to overcome the iniiuence of said control means on the rst of said devices only to render it conductive, means responsive to the conductivity of each device for reducing the innuence of said control means on each of the succeeding devices so that each device is rendered conductive by said opposing means only when all of the preceding devices are simultaneously conductive, and coupling means interconnecting said devices, said coupling means being eiective momentarily as each device is rendered conductive to render all of the preceding devices tem porarily non-conductive.

13. Apparatus according to claim 12 in which the coupling means comprises a capacitor and an asymmetric conductor connected in series between a principal electrode of each device and the corresponding electrode of the succeeding device of said series.

14. Apparatus according to claim 12 in which the coupling means comprises a capacitor and a dry rectier connected in series between a principal electrode of each device and the corresponding electrode .of the succeeding device of said series of devices said rectiiier offering its lowest resistance to current iiowing toward the succeeding device.

on a certain event occurring a predetermined number of times, the combination comprising a source of direct current, a series of electric discharge devices of the arc-like type connected in parallel circuits across said source, control means tending to maintain said devices nonconductive, said control means exerting a stronger inuence on each device after the first of said series than on the preceding device, means responsive to each occurrence of said event for opposing said control means, said opposing means being suiicient to overcome the iniiuence of said control means on the iirst of said devices only to render it conductive, means responsive to the conductivity of each device forireducing the influence of said control means on each of the succeeding devices so that each device after the rst is rendered conductive by said opposing means when all of the preceding devices are simultaneously conductive, means coupling said devices together and operable momentarily as each device is rendered conductive to render all of the preceding devices temporarily non-conductive, a clearing valve connected across said source in a circuit in parallel with said parallel circuits, said clearing valve being an electric discharge device ofthe arclike type associated with said control means to be rendered conductive by said opposing means when all of said series of devices are simultaneously conductive, means for coupling said clearing valve to the last device of said series so that all of the devices in said series are rendered -non-conductive upon said clearing valve becoming conductive and said clearing valve is rendered non-conductive upon said last device again becoming conductive, and means for effecting an operation of said work apparatus each time said clearing valve becomes conductive.

17. Apparatus according to claim 12 in which the coupling means comprises a capacitor and an asymmetric conductor connected in series between a principal electrode of each device and the corresponding electrode of the succeeding device of said series, and which includes an electric discharge clearing valve of the arc-like type having a pair of principal electrodes connected 1n an individual circuit across said source, said valve being associated with said control means to be rendered conductive by said opposing means when all of said series of devices are simultaneously conductive, a second capacitor connected between a principal electrode of said valve and the corresponding electrode of the last device ci said series, said second capacitor being momentarily eiective to render all of said series of devices non-conductive when said valveis rendered conductive and to eilect extinguishment of said valve when said last device is again rendered conductive, a work apparatus, and means for operating said work apparatus in response to current nowing through said valve.

18. In apparatus lfor counting a plurality oi.' electric potential impulses, a plurality of electric discharge devices responsive to each of said impulses, and interconnecting means between said discharge devices providing for the response of a diiierent one ox' a diil'erent combination of any number of said discharge devices to a series of successive impulses.

19. In apparatus for counting a plurality of electric potential impulses, a plurality of electric discharge devices responsive to each of said iml pulses, interconnecting means between said discharge devices providing for the response of a diierent one or a diiierent combination of any number n of said discharge devices to a series ROBERT W. PEARSON. SLAVO J. MURCEK. 

